CNN's public relations team responded to Trump's tweet, citing
cumulative numbers from Nielsen Media Research. Cumulative
numbers measure audience reach, while ratings — the statistic
Trump referred to — measure the average number of people watching
a given program.

"According to Nielsen cumulative numbers, 34 million people
watched CNN's inauguration day coverage on television. 34 million
watched Fox News," the CNN communications account said in a tweet, which was shared thousands of times
and became the basis of several news stories.

The cumulative number is technically correct. (CNN, however,
rounded it. The precise numbers show Fox News with 34.4 million
viewers and CNN with 34.2 million.) But it's a statistic that's
rarely, if ever, used in the cable news industry, according to
experts.

"It's a factual statistic, but I literally never used cumulative
ratings once when I edited TVNewser," Brian Flood, a media
reporter at TheWrap, told Business Insider in an email. "Not
once."

Instead, it's most common for networks to provide ratings for a
specific hour or program to boast about their audiences. That's
the spot where Fox News handily outpaced CNN throughout
Inauguration Day.

Take a look at some of the numbers from Nielsen:

Noon to 12:30 p.m. (oath of office and inaugural
address):

CNN: 3.375 million total viewers
Fox News: 11.768 million total viewers

11 a.m. to 1 p.m.

CNN: 3.047 million total viewers
Fox News: 10.483 million total viewers

1 p.m. to 5 p.m.

CNN: 2.326 million total viewers
Fox News: 7.901 million total viewers

Primetime (8 p.m. to 11 p.m.)

CNN: 4.528 million total viewers
Fox News: 6.958 million total viewers

Those numbers make it clear that Fox News easily outpaced CNN in
inauguration ratings, almost tripling CNN's numbers at some
points in the day.

"CNN ranked a strong #2 in cable news during the Inauguration of
President Donald Trump yesterday, January 20th," the release
said.

Erik Wemple, a media critic for The Washington Post, said that he
had "seen some of the silliness" over the ratings and that cable
news networks often engage in "puerile spats" over such things.
But he said that this time, CNN perhaps escalated it further than
normal.

"When there's a fact-check of the president, it moves away from
the realm of standard cable-news bickering," he told Business
Insider in an email.